Loading dll files in java

Loading dll files in java

There are several ways to make it possible for the Java runtime to find and load a dynamic library (DLL) at runtime. I will list them briefly here, followed by examples and further explanation below.

1. Call System.load to load the DLL from an explicitly specified absolute path.
2. Copy the DLL to one of the paths already listed in java.library.path
3. Modify the PATH environment variable to include the directory where the DLL is located.
4. Specify the java.library.path on the command line by using the -D option.
5. If using Eclipse, set the java.library.path in Eclipse for development/debugging.

Note: To help resolve an UnsatisfiedLinkError Runtime Error, see How to Handle the UnsatisfiedLinkError Runtime Error in Java

1. Call System.load to load the DLL from an explicitly specified absolute path.

This choice removes all uncertainty, but embeds a hard-coded path within your Java application. Example:

import com.chilkatsoft.CkZip; public class Test < static < try < System.load("C:/chilkatJava/chilkat.dll"); > catch (UnsatisfiedLinkError e) < System.err.println("Native code library failed to load.\n" + e); System.exit(1); >> public static void main(String argv[]) < CkZip zip = new CkZip(); System.out.println(zip.version()); >>

2. Copy the DLL to one of the paths already listed in java.library.path

To see the current value of the PATH environment variable, open a MS-DOS prompt and type:

Another way of viewing the java.library.path is to run this Java code:

String property = System.getProperty(«java.library.path»); StringTokenizer parser = new StringTokenizer(property, «;»); while (parser.hasMoreTokens())

Note: The java.library.path is initialized from the PATH environment variable. The directories may be listed in a different order, and the current directory «.» should be present in java.library.path, but may not be listed in the PATH environment variable.

The loadLibrary method may be used when the directory containing the DLL is in java.library.path. To load «chilkat.dll», call System.loadLibrary(«chilkat»), as shown here:

import com.chilkatsoft.CkZip; public class Test < static < try < System.loadLibrary("chilkat"); > catch (UnsatisfiedLinkError e) < System.err.println("Native code library failed to load.\n" + e); System.exit(1); >> public static void main(String argv[]) < CkZip zip = new CkZip(); System.out.println(zip.version()); >>

3. Modify the PATH environment variable to include the directory where the DLL is located.

Do this by modifying the PATH environment variable from the Windows Control Panel.

1. Start -> Control Panel -> System -> Advanced
2. Click on Environment Variables, under System Variables, find PATH, and click on it.
3. In the Edit windows, modify PATH by adding the location of the class to the value for PATH. If you do not have the item PATH, you may select to add a new variable and add PATH as the name and the location of the class as the value.
4. Close the window.
5. Reopen Command prompt window, and run your java code.

1. Right click «My Computer» icon
2. Choose «Properties» from context menu
3. Click «Advanced» tab («Advanced system settings» link in Vista)
4. In the Edit windows, modify PATH by adding the location of the class to the value for PATH. If you do not have the item PATH, you may select to add a new variable and add PATH as the name and the location of the class as the value.
5. Reopen Command prompt window, and run your java code.

Important: Setting the PATH environment variable from a MS-DOS command prompt has no effect on java.library.path. For example, this does not work:

set PATH=c:\chilkatJava;%PATH% java Test

Also, modifying the java.library.path from within Java code does not work either:

static < try < // Adding a directory to java.library.path here will not change anything. // System.loadLibrary will still look in the directories listed in java.library.path // as it existed at the very start of the program. // The extra directory path added to java.library.path will not // be searched by loadLibrary. String libpath = System.getProperty("java.library.path"); libpath = libpath + ";C:/chilkatJava"; System.setProperty("java.library.path",libpath); System.loadLibrary("chilkat"); >catch (UnsatisfiedLinkError e) < System.err.println("Native code library failed to load.\n" + e); System.exit(1); >>

4. Specify the java.library.path on the command line by using the -D option.

java -Djava.library.path=c:\chilkatJava TestApp

5. If using Eclipse, set the java.library.path in Eclipse for development/debugging.

1. Open Project->Properties, select «Java Build Path», click on the «Add External JARs. » button and add the «chilkat.jar»
2. (still within the Project Properties dialog) Click on the «Run/Debug Settings», select your Java class, then click on the «Edit. » button. Select the «Arguments» tab, then add -Djava.library.path=»C:\chilkatJava;$» where «C:\chilkatJava» is the directory path containing the «chilkat.dll» file.

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Loading DLL in Java

Solution: To load libraries, such as DLLs, you should use Where is the name of the library. Any further linker errors could be from dependency problems with finding other DLLs.

Loading DLL in Java

I am trying to load a dll in java using the following code System.loadLibrary(«mydll»);

The project is placed in D:\development\project\ and i have placed the dll on D:. I then gave following VM argument in eclipse configuration -Djava.library.path=D:/

But when i run i get UnsatisifiedLinkerError . After googling a bit, I used System.load(«D:\mydll.dll»);

but again getting the same problem, could someone can help?

Where you specify the dll filename in the library path, omit that. Additionally, your System.loadLibrary call should just be ‘mydll’. I can tell you (from experience) that if you put the DLL in the root of your project in Eclipse (i.e., D:\Eclipse Workspace\Proj), it should work. Any further linker errors could be from dependency problems with finding other DLLs. The exception is the same. Use something like Dependency Walker (http://www.dependencywalker.com/) to see if your DLL relies on anything else not on the system library path.

Edit: UnsatisfiedLinkError : Thrown if the Java Virtual Machine cannot find an appropriate native-language definition of a method declared native — it seems like you are using a JNI function which does not exist.

One problem you have is: System.load(«D:\mydll.dll»); should be System.load(«D:\\mydll.dll»); or System.load(«D:/mydll.dll»);

I have had more success with System.load, but loadlibrary is better designed for multiplatform. It figures out the extension for you.

Check out how to properly set up the native dependencies here. Additionally, make sure you use the correct JVM: in my case, the DLL was not found because it was a 32 bit DLL, but I used the x64 JVM!

Using System.loadLibrary(«mydll») works fine, you can also use that one. If you used javah and you think with your DLL everything is fine, there are two possibilies:

1. The JVM does not find your DLL : In this case, your java library path is not correct (which I doubt) and you should probably set it to . and place your DLL in the current working dir.
2. The JVM does not find a DLL your DLL depends on : If you have any dependent libraries in your DLL, they are NOT searched by the JVM, but by Windows itself. And Windows does not know the java.library.path , so it will look in the system PATH variable for those. If you have the possibility, you can set the system PATH variable to the location of your DLLs before starting the JVM and everything will be fine. Or you can load all your DLLs using the JVM like this

Java — Load DLL (using JNA) inside an OSGi bundle, The problem is the specialised JNA loadLibrary call, which is not OSGi aware. When you invoke loadLibrary from an OSGi bundle, it will use the OSGi classloader (which is bundle aware) to find where the DLL is, and in this case, extract it out from the bundle and make it loadable via the System.loadLibrary () …

Loading DLL file in java

While loading a dll file, using System.loadLibrary method, in a RCP application, it’s working as long as I am launching the application from Eclipse itself. But when exporting the RCP application and launching from the exported code, I am getting this exception :

ERROR - Native code library failed to load. See the chapter on Dynamic Linking Problems in the SWIG Java documentation for help. Try using a 32 bit JRE also. java.lang.UnsatisfiedLinkError: D:\ExportTest\eclipse\plugins\\ext\securityinterfaceX86\SecurityInterface-x86.dll: Can't find dependent libraries 

You are loading a 32bit C++ binary from a 64 bit JVM. You need to either use a 32 bit JVM or go for a mixed mode JVM. Use the same JRE that your Eclipse uses and you will be fine.

Multithreading — Unloading dll in Java, Java <->Loader <->Function. The loader is effectively just an interface, proxying the actual method calls to function, so function is never in direct contact with java. That way you would control in C/C++/whateva when function is loaded. This is interesting, let us know how it works! – Martin Algesten Nov 30, …

How to load dependent dlls in Java?

I have two dlls, C:\foo\x.dll and C:\bar\y.dll , where x.dll depends on y.dll (i.e. the implementation of functions in x will call functions in y).

In a Java application, when I load x.dll using JNA what do I need to set up to ensure that I don’t get a UnsatisfiedLinkException ?

I’m currently setting up jna.library.path to C:\foo , but it seems that it is not enough. Including both C:\foo and C:\bar in java.library.path also doesn’t help.

You can usually call System.load(«/name.dll») with the path to your dependent library prior to making the JNA call to load the primary.

System.loadLibrary(«name») will work if the library is on java.library.path and conforms to expected naming conventions.

Loading DLL file in java, While loading a dll file, using System.loadLibrary method, in a RCP application, it’s working as long as I am launching the application from Eclipse itself. But when exporting the RCP application and launching from the exported code, I am getting this exception : ERROR — Native code library failed to load. See …

Can’t load a .dll with System.load(path)

I made a Java OCR program using the aspriseOCR. It requires a .dll called AspriseOCR.dll, I copied the dll to C:/Windows/System32/ But when I use

System.load("C:/Windows/System32/AspriseOCR.dll"); 

I still get a UnsatisfiedLinkError.

I’ve spent the last 2 days searching for a solution to my problem, but I couldn’t find anything that works.

Okay everyone, it works now. Turns out I also had to make a 32-bit version! If anyone ever needs help with the OCR Engine from Asprise, pm and I’ll try to help you!

To load libraries, such as DLLs, you should use

Where «libname» is the name of the library. You do not include the extension of the file it is stored in, or the full path to the file. For your case, you would probably call

 System.loadLibrary("AspriseOCR"); 

to load the library you are using.

Because loadLibrary takes a library name for an argument, not a file, you must be careful where you place the .dll. Normally, you could include it in the working directory of the application, or in a native folder such as System32. If you must put it somewhere else, be sure to appropriately set java.libary.path . For example, if the .dll is in the folder «libraries», you should launch java with the argument

 -Djava.library.path=libraries 

How to configure .dll file in Java?, When you use System.loadLibrary() don’t include the .dll at the end. Also, if you are not setting java.library.path to point to the folder containing the DLL then the DLL should be in the directory where you …

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